Dequeue in Data Structure

Example: Program for Double Ended Queue (Dequeue)

#include<stdio.h>
#include<stdlib.h>
#define MAX 30

typedef struct dequeue
{
    int data[MAX];
    int rear,front;
}dequeue;

void initialize(dequeue *p);
int empty(dequeue *p);
int full(dequeue *p);
void enqueueR(dequeue *p,int x);
void enqueueF(dequeue *p,int x);
int dequeueF(dequeue *p);
int dequeueR(dequeue *p);
void print(dequeue *p);

void main()
{
    int i,x,op,n;
    dequeue q;     
    initialize(&q);     
    do
    {
     printf("\n1.Create\n2.Insert(Rear)\n3.Insert(Front)\n4.Delete(Rear)\n5.Delet(Front)");
        printf("\n6.Print\n7.Exit\n\nEnter your choice:");
        scanf("%d",&op);
        
        switch(op)
        {
            case 1: printf("\nEnter number of elements:");
                    scanf("%d",&n);
                    initialize(&q);
                    printf("\nEnter the data:");                     
                    for(i=0;i<n;i++)
                    {
                        scanf("%d",&x);
                        if(full(&q))
                        {
                            printf("\nQueue is Full!!");
                            exit(0);
                        }
                        enqueueR(&q,x);
                    }
                    break;
                    
            case 2: printf("\nInsert Element : ");
                    scanf("%d",&x);                             
                    if(full(&q))
                    {
                        printf("\nQueue is Full!!");
                        exit(0);
                    }                     
                    enqueueR(&q,x);
                    break;
                            
            case 3: printf("\nInsert Element :");
                    scanf("%d",&x);                             
                    if(full(&q))
                    {
                        printf("\nQueue is Full!!");
                        exit(0);
                    }                     
                    enqueueF(&q,x);
                    break;
                            
            case 4: if(empty(&q))
                    {
                        printf("\nQueue is Empty!!");
                        exit(0);
                    }                             
                    x=dequeueR(&q);
                    printf("\n Deleted Element is %d\n",x);
                    break;
                    
            case 5: if(empty(&q))
                    {
                        printf("\nQueue is Empty!!");
                        exit(0);
                    }                             
                    x=dequeueF(&q);
                    printf("\nDeleted Element is %d\n",x);
                    break;
                            
            case 6: print(&q);
                    break;
                    
            default: break;
        }
    }while(op!=7);
}  
void initialize(dequeue *P)
{
    P->rear=-1;
    P->front=-1;
}  
int empty(dequeue *P)
{
    if(P->rear==-1)
        return(1);
    
    return(0);
}  
int full(dequeue *P)
{
    if((P->rear+1)%MAX==P->front)
        return(1);
    
    return(0);
}  
void enqueueR(dequeue *P,int x)
{
    if(empty(P))
    {
        P->rear=0;
        P->front=0;
        P->data[0]=x;
    }
    else
    {
        P->rear=(P->rear+1)%MAX;
        P->data[P->rear]=x;
    }
}  
void enqueueF(dequeue *P,int x)
{
    if(empty(P))
    {
        P->rear=0;
        P->front=0;
        P->data[0]=x;
    }
    else
    {
        P->front=(P->front-1+MAX)%MAX;
        P->data[P->front]=x;
    }
}  
int dequeueF(dequeue *P)
{
    int x;     
    x=P->data[P->front];     
    if(P->rear==P->front)    //delete the last element
        initialize(P);
    else
        P->front=(P->front+1)%MAX;     
    return(x);
}   
int dequeueR(dequeue *P)
{
    int x;     
    x=P->data[P->rear];     
    if(P->rear==P->front)
        initialize(P);
    else
        P->rear=(P->rear-1+MAX)%MAX;         
    return(x);
}  
void print(dequeue *P)
{
    if(empty(P))
    {
        printf("\nQueue is empty!!");
        exit(0);
    }     
    int i;
    i=P->front;     
    while(i!=P->rear)
    {
        printf("\n%d",P->data[i]);
        i=(i+1)%MAX;
    }     
    printf("\n%d\n",P->data[P->rear]);
}